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November 29, 2022, 12:01:49 AM

Author Topic: Monamour 2A3-40 with Harbeth SHL5  (Read 95 times)

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Offline ianm0

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Monamour 2A3-40 with Harbeth SHL5
« on: November 24, 2022, 03:13:37 PM »
My listening room is about 4.2*7*0.85 m. I listen to classical music mainly and seldom louder than 80 db - most of the time 70-75 db - at the listening position. Wonder if the 2A3-40 will adequately drive the Harbeth SHL5, even for big orchestral music?
What tubes are supplied with the kit when available?

[Edit] Perhaps I should add that now I am using push-pull KT88 Triode mode biased for an output of about 18W (estimate). Occasionally it runs out of steam at very demanding passages. Otherwise I am quite happy. Just have the itch to try out SET for a change.
« Last Edit: November 24, 2022, 06:42:04 PM by ianm0 »

Offline Tom-s

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Re: Monamour 2A3-40 with Harbeth SHL5
« Reply #1 on: November 25, 2022, 03:27:37 AM »
My listening room is about 4.2*7*0.85 m.

That's a very interesting size! :-)

Other than that. The MonAmour (assuming it gets to 6-8W with reasonable distortion) will get your 86db/w/m speakers up to a theoretical 95db. It could be this is adequate for low listening levels. And it probably is for 95% of the time.
But with big orchestral pieces, having lots of dynamics, you just may notice it on some passages.
If you're happy with the 18w from the KT88 now; you'll be ok with 8w SE probably.
If you think your KT88 is not adequate at the moment. I'd look into another kind of power (like 40-80w tube amp).

Offline Paul Birkeland

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Re: Monamour 2A3-40 with Harbeth SHL5
« Reply #2 on: November 25, 2022, 06:59:59 AM »
Wonder if the 2A3-40 will adequately drive the Harbeth SHL5, even for big orchestral music?
If you have a 3.5W 2A3 amp and you plug a JJ 2A3-40 into it, you'll still have a 3.5W 2A3 amp. 

It is possible to do a highly customized circuit around the 2A3-40 to get more like 19W out, but that requires a three stage amplifier and direct coupling between the 300B and the stage before it.

We have been working on a 30W or so SET amp kit for some time that would be a good fit for what you're up to.
Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man

Offline Tom-s

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Re: Monamour 2A3-40 with Harbeth SHL5
« Reply #3 on: November 25, 2022, 07:57:55 AM »
Luckily Bottlehead has a solution to this shortcoming PB pointed out:
Quote from: Bottlehead MonAmour product page
By popular request! MonAmour is our finest high quality single ended, parallel feed, directly heated triode monoblocks pair amplifier kit, with a capability of 4.5 watts output per channel with vintage 2A3s and up to as high as 7 watts output with modern 2A3s like the JJ2A3-40 and Sovtek 2A3.

Offline ianm0

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Re: Monamour 2A3-40 with Harbeth SHL5
« Reply #4 on: November 26, 2022, 06:24:29 PM »
If you have a 3.5W 2A3 amp and you plug a JJ 2A3-40 into it, you'll still have a 3.5W 2A3 amp. 

It is possible to do a highly customized circuit around the 2A3-40 to get more like 19W out, but that requires a three stage amplifier and direct coupling between the 300B and the stage before it.

We have been working on a 30W or so SET amp kit for some time that would be a good fit for what you're up to.

Really looking forward to that. My understanding of 2A3-40 is a cross between 300B and 2A3 - best of both worlds (?) - with more power. Hope it's going to be a monoblock design like the MonAmour.

Offline Paul Birkeland

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Re: Monamour 2A3-40 with Harbeth SHL5
« Reply #5 on: November 26, 2022, 08:02:23 PM »
The 2A3-40 is a 300B with a 2.5V filament instead of a 5V filament.  Still, without circuit and iron changes, your standard 2A3 amp won't make any more power with the 2A3-40 plugged in.

Yes, a higher power amp will get too heavy as a stereo amp, so monoblocks are really the only choice.
Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man